Ni-pt alloy and target comprising the alloy

ABSTRACT

The present invention provides a Ni—Pt alloy superior in workability containing Pt in a content of 0.1 to 20 wt % and having a Vickers hardness of 40 to 90, and a target comprising the Ni—Pt alloy. The present invention also provides a manufacturing method of Ni—Pt alloy superior in workability comprising a step of subjecting a raw material Ni having a purity of 3N level to electrochemical dissolution, a step of neutralizing the electrolytically leached solution with ammonia, a step of removing impurities through filtration with activated carbon, a step of blowing carbon dioxide into the resultant solution to form nickel carbonate and exposing the resultant product to a reducing atmosphere to prepare high purity Ni powder, a step of leaching a raw material Pt having a purity of 3N level with acid, a step of subjecting the leached solution to electrolysis to prepare high purity electrodeposited Pt, and a step of dissolving the resultant high purity Ni powder and high purity electrodeposited Pt. The foregoing method enables the rolling of the Ni—Pt alloy ingot upon reducing the hardness thereof, which results in the stable and efficient manufacture of a rolled target.

TECHNICAL FIELD

The present invention relates to a Ni—Pt alloy superior in workability,a sputtering target manufacturing by rolling a Ni—Pt alloy ingot, and amanufacturing method of such Ni—Pt alloy and Ni—Pt alloy target.

BACKGROUND ART

Ni—Pt is used as a sputtering target for semiconductor devices, and thisNi—Pt target was conventionally manufactured with the powder metallurgyprocess. In other words, the target was manufactured by sintering Nipowder and Pt powder, or by sintering Ni—Pt alloy powder.

Since it is impossible for a sintered product to become a 100% highdensity product, it is undeniable that such sintered product is inferiorin terms of density in comparison to a target manufactured via melting,casting and rolling.

Therefore, gas components easily get mixed into the target, and not onlydoes this reduce purity, it causes abnormal electrical discharge duringsputtering, induces the generation of particles, and deteriorates thedeposition characteristics.

Meanwhile, a Ni—Pt product formed via melting and casting has a problemin that it is extremely hard and brittle. As a result, when a Ni—Ptingot is rolled, there is a problem in that grain boundary fracturesoccur, and it is not possible to manufacture a flat and even planartarget. This is the reason targets were manufactured with the powdermetallurgy process as described above.

In light of the foregoing circumstances, a Ni—Pt target formed viamelting and casting, and which is free from cracks, has been proposed(for instance, refer to Patent Document 1).

This Patent Document 1 considered the cause of fractures to be thecoarsened crystal grains in the target and, in order to obtain finecrystal grains, attempted to inhibit the coarsening of crystals bypreparing a mold with large heat capacity or a water-cooled mold, andperforming rapid quenching by inhibiting the temperature rise of themold.

Nevertheless, with Patent Document 1, there is a drawback in that largeequipment is necessary for preparing a mold with large heat capacity ora water-cooled mold, and there is a problem in that it is difficult toinhibit the coarsening of crystals unless the cooling speed isconsiderably fast.

Further, the crystals that come in contact with the mold are fine, andbecome coarse as they draw away from such mold. Thus, there is a problemin that it is difficult to obtain a uniform crystal structure, and it istherefore not possible to manufacture a target having a uniformstructure or that is stable.

-   [Patent Document 1] Japanese Patent Laid-Open Publication No.    S63-33563

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide technology capable ofrolling a Ni—Pt alloy ingot upon reducing the hardness thereof, andmanufacturing a rolled target stably and efficiently.

In order to overcome the foregoing problems, the present inventorsdiscovered that by increasing the purity of the Ni—Pt alloy, it ispossible to significantly reduce the hardness of the Ni—Pt alloy ingot.

Based on the foregoing discovery, the present invention provides 1) aNi—Pt alloy superior in workability containing Pt in a content of 0.1 to20 wt % and having a Vickers hardness of 40 to 90, and a targetcomprising the Ni—Pt alloy, and 2) the Ni—Pt alloy and Ni—Pt alloytarget according to 1) above having a purity of 99.99% or higher.

Further, the present invention also provides 3) a manufacturing methodof Ni—Pt alloy superior in workability comprising a step of subjecting araw material Ni having a purity of 3N level to electrochemicaldissolution, a step of neutralizing the electrolytically leachedsolution with ammonia, a step of removing impurities by filtering theneutralized solution with activated carbon, a step of blowing carbondioxide into the resultant solution to form nickel carbonate andexposing the resultant product to a reducing atmosphere to prepare highpurity Ni powder, a step of leaching a raw material Pt having a purityof 3N level with acid, a step of subjecting the leached solution toelectrolysis to prepare high purity electrodeposited Pt, and a step ofdissolving the resultant high purity Ni powder and high purityelectrodeposited Pt, 4) the manufacturing method of Ni—Pt alloyaccording to 3) above wherein the Ni—Pt alloy has a purity of 99.99% orhigher, and 5) the manufacturing method of Ni—Pt alloy superior inworkability according to 3) or 4) above, wherein the Ni—Pt alloy has Ptin a content of 0.1 to 20 wt % and has a Vickers hardness of 40 to 90Pt.

Further, the present invention also provides 6) the manufacturing methodof a Ni—Pt alloy target, wherein the dissolved Ni—Pt alloy ingotmanufactured based on any one of the methods according to 3) to 5)above.

EFFECT OF THE INVENTION

As a result, the present invention is able to easily perform coolrolling to a dissolved Ni—Pt alloy ingot without requiring anyequipment, such as preparing a mold with large heat capacity or awater-cooled mold, for accelerating the cooling speed in order toinhibit the coarsening of crystals, and yields a superior effect in thatit is possible to improve the quality of the Ni—Pt alloy deposition byreducing impurities contained in the Ni—Pt alloy target and realizinghigh purification.

Further, in addition to being able to prevent the generation offractures and cracks in the target, a significant effect is yielded inthat the generation of particles which often occurred in conventionalsintered targets and resulted from the abnormal electrical discharge ofsputtering can be inhibited.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention can be applied to a Ni—Pt alloy containing Pt in acontent of 0.1 to 20 wt %. This component composition is required in thedeposition of a Ni—Pt alloy material of semiconductor devices, and isalso a composition range of the Ni—Pt alloy or target of the presentinvention capable of reducing the hardness. The Vickers hardnessobtained by the Ni—Pt alloy of the present invention is 40 to 90.

When the Pt content contained in Ni increases, the hardness (Vickers Hv)also increases. This also has a significant influence on the amount ofimpurities. At 3N level, when the Pt content contained in Ni increases,the hardness increases drastically, and reaches approximately Hv 130 inthe vicinity of Ni-20 wt % Pt.

When an ingot is rolled under this kind of circumstance where thehardness is increased, fractures arise at the grain boundary as a matterof course.

Meanwhile, with the high purity Ni—Pt alloy of the present invention,although the hardness gradually increases from Pt 0.1 wt % to 20 wt %,the Vickers hardness is within the range of 40 to 90, and is within arange where cold rolling can be performed. This is a significant featureof the present invention.

If the hardness is less than Pt 0.1 wt %, sufficient characteristics asa Ni—Pt alloy cannot be obtained, and if the hardness exceeds Pt 20 wt%, as described above, the target becomes too hard and difficult toprocess. Thus, the Pt content is set to be 0.1 to 20 wt %.

As a result, in addition to being able to prevent the generation offractures and cracks in the target, a significant effect is yielded inthat the generation of particles which often occurred in conventionalsintered targets and resulted from the abnormal electrical discharge ofsputtering can be inhibited.

The Ni—Pt alloy and Ni—Pt alloy target of the present invention have apurity of 99.99% or higher. As a result, the Vickers hardness is withinthe range of 40 to 90, and is within a range where cold rolling can beperformed.

The manufacturing method of this kind of Ni—Pt alloy superior inworkability is explained; as for a Ni raw material, foremost, a rawmaterial Ni having a purity of 3N level is subject to electrochemicaldissolution, the electrolytically leached solution is thereafterneutralized with ammonia, and the neutralized solution is filtered withactivated carbon to remove impurities.

Next, carbon dioxide is blown into this resultant solution to obtainnickel carbonate, and this is subject to reducing atmosphere tomanufacture high purity Ni powder.

Meanwhile, as for Pt raw material, a raw material Pt having a purity of3N level is leached with acid, and this leached solution is subject toelectrolysis to manufacture high purity electrodeposited Pt.

Next, the high purity Ni powder and high purity electrodeposited Ptobtained above are dissolved. The obtained Ni—Pt alloy has a purity of99.99% (4N) or higher.

Further, the Ni—Pt alloy ingot obtained via melting and casting asdescribed above has a Pt content of 0.1 to 20 wt % and a Vickershardness of 40 to 90. Also as described above, this ingot is superior inworkability.

As a result of performing cold rolling to this dissolved Ni—Pt alloyingot manufactured as described above, it is possible to easilymanufacture a Ni—Pt alloy target.

Thus, in addition to being able to prevent the generation of fracturesand cracks in the target, a significant effect is yielded in that thegeneration of particles which often occurred in conventional sinteredtargets and resulted from the abnormal electrical discharge ofsputtering can be inhibited.

EXAMPLES

Examples of the present invention are now explained. These Examples aremerely illustrative, and the present invention shall in no way belimited thereby. In other words, the present invention shall only belimited by the scope of the present invention, and shall include thevarious modifications other than the Examples of this invention.

Example 1

10 kg of 3N level Ni raw material shown in Table 1 was used as theanode, and this was subject to electrolytic leaching with hydrochloricacid solution. At the point when it became 100 g/L, the resultantsolution was neutralized with ammonia, and pH was set to 8. Thisresultant solution was filtered by adding 10 g/L of activated carbon toremove impurities.

Next, carbon dioxide was blown into this resultant solution to obtainnickel carbonate. The resultant solution was subject to heat treatmentat a temperature of 1200° C. under H₂ atmosphere to obtain 8 kg of highpurity Ni powder.

Meanwhile, 5 kg of 3N level Pt was used and dissolved in royal water.The resultant solution was made to be a pH 2 level, and this was subjectto electrolytic winning to obtain high purity electrodeposited Pt.Carbon was used as the anode during electrolytic winning.

The high purity Ni powder and high purity electrodeposited Pt obtainedas described above were dissolved under a vacuum where the degree ofvacuum was 10⁻⁴ Torr to obtain high purity Ni-20% Pt alloy. The hardnessof this alloy was Hv 80. This alloy was rolled at room temperature toobtain a target.

There were no generation of cracks or fractures in the target, androlling could be performed easily. The results are shown in Table 1.TABLE 1 (wtppm) Compar- Raw Raw High High Exam- ative Material MaterialPurity Purity ple Example Ni Pt Ni Pt 1 1 Fe 110 10 2.1 1.0 1.7 90 Cr 502 0.6 0.5 0.6 44 Co 60 5 0.5 0.2 0.4 49 Cu 30 4 0.1 0.1 0.1 25 Al 10 80.1 0.1 0.1 9.5 O 150 70 20 <10 10 130 C 80 20 10 <10 10 70 N 30 10 <10<10 <10 25 Hardness 100 40 70 30 80 110 Plastic Fair Good Good Excel-Excel- Infe- Workability lent lent rior at Room Temperature

Example 2

As with Example 1, high purity Ni-0.5% Pt alloy was prepared. Thehardness of this alloy was Hv 45. This alloy was rolled at roomtemperature to obtain a target. There were no generation of cracks orfractures in the target, and rolling could be performed easily. Theresults are shown in Table 2.

Example 3

As with Example 1, high purity Ni-5% Pt alloy was prepared. The hardnessof this alloy was Hv 55. This alloy was rolled at room temperature toobtain a target. There were no generation of cracks or fractures in thetarget, and rolling could be performed easily. The results are shown inTable 2.

Example 4

As with Example 1, high purity Ni-10% Pt alloy was prepared. Thehardness of this alloy was Hv 65. This alloy was rolled at roomtemperature to obtain a target. There were no generation of cracks orfractures in the target, and rolling could be performed easily. Theresults are shown in Table 2. TABLE 2 (wtppm) Example 2 Example 3Example 4 Fe 2.0 1.9 1.8 Cr 0.6 0.6 0.6 Co 0.5 0.5 0.5 Cu 0.1 0.1 0.1 Al0.1 0.1 0.1 O 20 20 20 C 10 10 10 N <10 <10 <10 Hardness 45 55 65Plastic Workability at Excellent Excellent Excellent Room Temperature

Comparative Example 1

Pt having the same purity as 3N level Ni was dissolved to become Ni-20wt %. As a result, the hardness of the obtained ingot was Hv 110. Thisingot was extremely hard, and plastic working at room temperature wasdifficult. The results are shown in Table 1 in comparison to Example 1.

INDUSTRIAL APPLICABILITY

As described above, the present invention yields a superior effect inthat it is easy to perform cold rolling to a dissolved Ni—Pt alloyingot, and is capable of simultaneously reducing the impuritiescontained in the Ni—Pt alloy target to realize high purification. As aresult, it is possible to improve the quality of Ni—Pt alloy deposition.

Further, in addition to being able to prevent the generation offractures and cracks in the target, a significant effect is yielded inthat the generation of particles resulting from the abnormal electricaldischarge of sputtering can be inhibited. Therefore, this is suitablefor the deposition of Ni—Pt alloy in a semiconductor device.

1. A Ni—Pt alloy superior in workability containing Pt in a content of0.1 to 20 wt % and having a Vickers hardness of 40 to
 90. 2. The Ni—Ptalloy according to claim 1 having a purity of 99.99% or higher.
 3. Amethod of manufacturing Ni—Pt alloy superior in workability, comprisingthe steps of: subjecting a raw material Ni having a purity of 3N levelto electrochemical dissolution, neutralizing the electrolyticallyleached solution with ammonia, removing impurities by filtering theneutralized solution with activated carbon, blowing carbon dioxide intothe resultant solution to form nickel carbonate and exposing theresultant product to a reducing atmosphere to prepare high purity Nipowder, leaching a raw material Pt having a purity of 3N level withacid, subjecting the leached solution to electrolysis to prepare highpurity electrodeposited Pt, and dissolving the resultant high purity Nipowder and high purity electrodeposited Pt.
 4. The method according toclaim 3, wherein the Ni—Pt alloy has a purity of 99.99% or higher. 5-6.(canceled)
 7. A Ni—Pt alloy target superior in workability containing Ptin a content of 0.1 to 20 wt % and having a Vickers hardness of 40 to90.
 8. The Ni—Pt alloy target according to claim 7 having a purity of99.99% or higher.
 9. A method according to claim 4, wherein the Ni—Ptalloy has Pt in a content of 0.1 to 20 wt % and has a Vickers hardnessof 40 to
 90. 10. A method according to claim 9, further comprising thestep of manufacturing a Ni—Pt alloy sputtering target from the highpurity Ni powder and high purity electrodeposited Pt after saiddissolving step.
 11. A method according to claim 3, wherein the Ni—Ptalloy has Pt in a content of
 0. 1 to 20 wt % and has a Vickers hardnessof 40 to
 90. 12. A method according to claim 11, further comprising thestep of manufacturing a Ni—Pt alloy sputtering target from the highpurity Ni powder and high purity electrodeposited Pt after saiddissolving step.
 13. A method according to claim 3, further comprisingthe step of manufacturing a Ni—Pt alloy sputtering target from the highpurity Ni powder and high purity electrodeposited Pt after saiddissolving step.